Concealed dangerous articles detection method and device

Abstract

A method and an apparatus for detecting hidden hazardous substance including the steps of: performing terahertz imaging for a detected object; judging whether there is a suspicious area containing the hidden hazardous substance in a terahertz image of the detected object obtained by the terahertz imaging; performing a multi-wavelength spectroscopy measurement to the suspicious area, determining whether the hazardous substance is contained in the suspicious area according to results of multi-wavelength spectroscopy measurement; and outputting the image of the detected object and hazardous substance detecting result. Also disclosed is an apparatus for implementing the method for detecting the hidden hazardous substance according to the present invention. Determination of the hidden hazardous substance can be performed from the perspectives of shape features and substance composition, thus the accuracy of detection is greatly increased.

The invention claimed is: 
     
       1. A method for detecting hidden hazardous substance, comprising the following steps:
 producing wavelength tunable continuous wave terahertz radiation for irradiating a detected object and interacting with the object by a terahertz emitting device; 
 receiving terahertz radiation reflected back from the detected object by a terahertz detector; 
 collimating a wave beam produced by the terahertz emitting device and focusing the wave beam to the detected object, meanwhile, collecting a terahertz wave beam reflected back from the detected object to the terahertz detector by a terahertz optical assembly; 
 adjusting a spatial position of the terahertz wave beam incident to the detected object by a wave beam scanning control system; and 
 controlling coordination of the terahertz emitting device, the terahertz detector and the wave beam scanning control system in an apparatus, building a terahertz reflection image of the detected object, judging whether there is a suspicious area containing hazardous substance in the terahertz reflection image based on shape characteristics and gray-scale value characteristics obtained by the terahertz reflection image, searching and locating the suspicious area, performing analysis and processing for multi-wavelength reflection spectrum data of measurement points of interest in the suspicious area, and presenting a hazardous substance identifying result by a data acquisition and processing system. 
 
     
     
       2. The method according to  claim 1 , further comprising:
 adjusting the terahertz emitting device to operate at an imaging wavelength; 
 collecting the terahertz radiation reflected back by the detected object through the terahertz detector to obtain information of one pixel point of the detected object; and 
 enabling the terahertz wave beam to scan each pixel in a field of vision through the wave beam scanning control system so as to acquire the terahertz reflection image of the detected object. 
 
     
     
       3. The method according to  claim 2 , wherein the step of adjusting the terahertz emitting device to operate at an imaging wavelength further comprises:
 a) selecting a frequency window with good transmittance according to transmission properties of the terahertz radiation in the atmosphere, and determining an operating wavelength range of a terahertz radiation source; 
 b) comprehensively analyzing a transmitting power of the terahertz radiation source and an influence of the wavelength on an imaging signal-to-noise ratio and a spatial resolution, and meanwhile taking into account the range of wavelength defined in step a) to determine an optimal imaging wavelength. 
 
     
     
       4. The method according to  claim 2 , wherein the wave beam scanning control system comprises a terahertz wave beam scanning device and a terahertz wave beam scanning control unit, the step of enabling the terahertz wave beam to scan each pixel in the field of vision through the wave beam scanning control system further comprises: enabling the terahertz wave beam scanning control unit to send a signal to the terahertz wave beam scanning device, and adjusting a wave beam scanning module in the terahertz wave beam scanning device to change a light spot position of the terahertz wave beam on the detected object. 
     
     
       5. The method according to  claim 4 , wherein the wave beam scanning module is a galvanometer mirror. 
     
     
       6. The method according to  claim 2 , wherein the wave beam scanning control system comprises a terahertz wave beam scanning device and a terahertz wave beam scanning control unit, the step of enabling the terahertz wave beam to scan each pixel in the field of vision through the wave beam scanning control system further comprises: the terahertz wave beam scanning device bearing a system comprised of the terahertz emitting device, the terahertz detector and the terahertz optical assembly to implement a translational movement, enabling the terahertz wave beam scanning control unit to send a signal to the terahertz wave beam scanning device, and adjusting the spatial position of the assembly to change a light spot position of the incident terahertz wave beam on the detected object. 
     
     
       7. The method according to  claim 1 , further comprising selectively adjusting a radiation wavelength of the terahertz emitting device through a wavelength tuning control unit to enable the terahertz emitting device to operate at a wavelength required by a multi-wavelength spectroscopy. 
     
     
       8. An apparatus for implementing a method for detecting hidden hazardous substance comprising:
 a terahertz emitting device configured to produce wavelength tunable continuous wave terahertz radiation for irradiating a detected object and interacting with the object; 
 a terahertz detector configured to receive terahertz radiation reflected back from the detected object; 
 a terahertz optical assembly configured to collimate a wave beam produced by the terahertz emitting device, and focus it to the detected object, and meanwhile collect a terahertz wave beam reflected back from the detected object to the terahertz detector; 
 a wave beam scanning control system configured to adjust a spatial position of the terahertz wave beam incident to the detected object; and 
 a data acquisition and processing system connected to the terahertz emitting device, the terahertz detector and the wave beam scanning control system and configured to control coordination of the terahertz emitting device, the terahertz detector and the wave beam scanning control system in an apparatus, build a terahertz reflection image of the detected object, judge whether there is a suspicious area containing hazardous substance in the terahertz reflection image based on shape characteristics and gray-scale value characteristics obtained by the terahertz reflection image, searching and locating the suspicious area, then perform analysis and processing for multi-wavelength reflection spectrum data of measurement points of interest in the suspicious area, and present a hazardous substance identifying result. 
 
     
     
       9. The apparatus according to  claim 8 , wherein the terahertz emitting device comprises a terahertz emitter and a wavelength tuning control unit, wherein the wavelength tuning control unit is connected to the terahertz emitter, to selectively adjust radiation wavelength of the terahertz emitter. 
     
     
       10. The apparatus according to  claim 9 , wherein the terahertz emitter is a Gunn oscillator and a frequency multiplier, a backward wave tube, a parameter oscillator, or a quantum cascade laser. 
     
     
       11. The apparatus according to  claim 9 , wherein the terahertz detector is a Schottky diode, a superconducting-insulator-superconducting junction frequency mixer, or a bolometer. 
     
     
       12. The apparatus according to  claim 8 , wherein the wave beam scanning control system comprises a terahertz wave beam scanning device and a terahertz wave beam scanning control unit, the terahertz wave beam scanning control unit is connected to the terahertz wave beam scanning device, the terahertz wave beam scanning device comprises a wave beam scanning module and is used to adjust and monitor the wave beam scanning module in real time to complete setting and reading of the wave beam spatial position information. 
     
     
       13. The apparatus according to  claim 12 , wherein the wave beam scanning module is a galvanometer mirror. 
     
     
       14. The apparatus according to  claim 12 , wherein the terahertz wave beam scanning device is a mechanical translational table which carries a system comprising the terahertz emitting device, the terahertz detector and the terahertz optical assembly and performs 2-dimensional point-by-point scanning of the detected object to obtain an image of the detected object. 
     
     
       15. The apparatus according to  claim 8 , wherein the terahertz optical assembly comprises a beam splitter which is responsible for collimating the wave beam produced by the terahertz emitting device and collecting the terahertz wave beam reflected back from the detected object to the terahertz detector, a planar mirror and a parabolic mirror or an elliptical mirror or lens for focusing the terahertz wave beam on the detected object.